Computational study of optoelectronic properties of oxadiazole-based compounds for organic light emitting diodes

Abstract

The electronic, charge transport properties and UV-visible electronic transitions of a series of oxadiazole-based compounds 1–8 were calculated using DFT and TD-DFT methods. HOMO–LUMO gaps, reorganisation energies, and injection barriers were calculated at the B3LYP/6-31G(d,p) level of theory. The photophysical properties were predicted at the TD-PBE0/6-31G(d,p) computational level. The obtained results put in evidence that the designed oxadiazole derivatives 2–8 are better charge transport materials compared to the experimental derivative 1 and the reference materials Alq3 and TPD. The calculated reorganisation energies show that derivatives 6 and 4 are predicted as the best electron transport materials; whereas 4 and 5 are predicted as the best hole transport materials. The low values of the calculated ionisation and hole extraction potentials suggest that 4 is the best molecule for hole injection; whereas the high values of the calculated electron affinities and electron extraction potentials reveal that 6 is the most suitable derivative for electron injection. Absorption and fluorescence transitions involve mainly LUMOs and HOMOs. The designed fluorophore 8, which has the highest Stokes shift values, could be used in OLED light-emission layers.